Process for the manufacture of aluminium fluoride



Patented Mar. 29, 1932 UNITED STATES PATENT ori ice MAX ZIMMERMANN, F LEVERKUSEN-ON-THE-RHINE, GERMANY, ASSIGNOR TO I, G.

FARBENINDUSTR-IE AKTIENG-ESELLSCHAF '1, OF

MANY, A CORPORATION OF GERMANY FRANKFORTONTHE MAIN, GER- IROOESS FOR THE MANUFAGTURE OF "ALUMINIUM FLUORIDE i No Drawing. Application filed December 16, 1929, Serial No. 414,595, and iniGermany December 31, 1928.,

The present invention relates to the manufacture of anhydrous or hydrated aluminium fluoride and consists in treating dry alumina or solid hydra-ted alumina with gaseous hydrofluoric acid at temperatures between about 0 and 400 C. V

The customary commercial process for the manufacture of aluminium fluoride consists in decomposing hydrated alumina by means 1 of aqueous hydrofluoric acid. By this means there is obtained a hydrated product, thedehydration of which is diflicult, since it readily loses hydrofluoric acid which, by attacking the walls of the containing vessel, introduces 5 impurities into the product.

It is also known that aluminium fluoride can be obtained from alumina or hydrated alumina by treatment with gaseous hydrofluoric acid, in which process the temperature must be raised to such a high degree that the aluminium fluoride distils or sublimes. In

every case known to me the description of this process of manufacture specifies a tempera ture equivalent to at least red heat, that means about 900 C.

This process has not found any technical application, since no material available for the containing vessels remains stable to hydrofluoric acid at the necessary temperatures. y

' In accordance with the present invention the technical manufacture of anhydrous or hydrated aluminium fluoride from dry alu-- process of this invention by effecting the treatment at room temperature, when arestill substantially below red heat, Say at 5.

about C. orosomewhat above, the water content decreases in. such a manner, that at 100 C; it amounts to about 6% and at C. to about 3%, while at 200 C. and above the aluminium fluoride is practically anhydrous.

Anhydrous or nearly anhydrous products are likewise obtainableby first producing at place in accordance the V room temperature a hydrated aluminium fluoride and raising the temperature towards the end of the reaction. The water content obtained at the various temperatures employed is the same as stated above.

According to a still further feature of th invention, instead of gaseous hydrofluoric acid,'there can also be employed a mixture of gaseous hydrofluoric acid and gaseous hydrochloric acid, such as is produced, for example, in the process of specification Ser. No. 414,594 filed Dec. 16, 1929. The favourable working temperature is about the same as when using gaseous hydrofluoric acid'alone. It is remarkable that, when using a mixture of hydrofluoric acid and hydrochloric acid vapors, only aluminium fluoride is obtained.

The invention is illustrated by the follow- EmampZe.-A current of gaseous, hydrofluoric acid is passed-over solid hydrated alui mina at room temperature until clouds of fume emerge from the end of the apparatus,"

Whilestill passing hydrofluoric acid through "80 ing example without being limited'thereto:

the vessel, the temperature is raised to about I 200 C. and, as soon as considerable quantities of hydrofluoric'acid again escape the re no action is complete.

Alternatively a mixture of hydrofluoric acid and hydrochloric acid vapors is used instead of hydrofluoric acid alone, the conditions of Working otherwise being as specified above. In this case also the mixed acids are passed through until substantial quantities of hydrofluoric acid vapor emerge from the end of the apparatus. In this manner aluminium'fluoride is obtained, the hydrofluoric acid content'of which fulfills or exceeds the customary commercial requirements;

I claim 7 1;. Process for preparing aluminium fluor ide comprising treating a compound of the group consisting of anhydrous alumina and solid hydrated alumina and mixtures thereof With gaseous hydrofluoric acid at temperatures of 'betvveen about 0 and lOO C.

2. Process for preparing aluminium fluoride comprlslng treating a compound ofthe group consisting of anhydrous alumina, solid I hydratedalumina and-mixtures. of anhydrous and solid hydrated alumina With gaseous hydrofluoric acid at first atatemperature of abou t 15 C. until themass is saturated With hydrofluoric acid, then raising the temperature to about 200 and continuing the introduction'ofgaseous hydrofluoric acid until the decomposition is complete. 7 I

Whereofilaflix my slgnature.

ln testimony MAX ZIlVIMERMANN.

, so, r 

